LED Current Balancing Circuit with Quasi-Resonant Flyback Control
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Solution Overview
Problem
Existing methods for controlling current through series connected light emitting diodes (LEDs) often fail to accurately balance currents in parallel strings and do not effectively manage overpower or open circuit conditions, leading to inefficiencies in applications such as backlighting and industrial uses.
Innovation Solution
A control system utilizing a transformer with a primary and secondary winding, a rectifier, and a quasi-resonant flyback control system that includes current sense circuits and zero crossing detection to regulate and balance currents across multiple strings of LEDs, ensuring equal current distribution and preventing damage from overpower conditions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If prior methods and circuits are used to control current through LED strings, then basic current control is achieved, but current balancing accuracy across parallel strings deteriorates
Solution Approach 1:
The patent implements feedback mechanisms through current sensing circuits that continuously monitor the current through each LED string and adjust the switching control accordingly. The controller receives feedback signals from current sensors and modifies the duty cycle of PWM signals to maintain equal current distribution across all parallel LED strings, resolving the contradiction between basic current control and accurate current balancing.
Solution Approach 2:
The patent replaces mechanical current adjustment methods with electronic control mechanisms. Instead of using physical rheostats or mechanical switches for current balancing, the system uses electronic PWM control with digital signal processing to achieve precise current regulation and balancing across multiple LED strings, significantly improving measurement and control accuracy.
2Reliability
If series switches are used to switch off current in one LED string, then open circuit protection is achieved, but current control accuracy deteriorates
Solution Approach 1:
The patent employs dynamic control mechanisms where the switching elements operate in a controlled manner rather than simple on/off states. The controller dynamically adjusts the duty cycle of PWM signals based on real-time feedback from current sensors, allowing for continuous current regulation even when protection modes are activated. This dynamic approach maintains current control accuracy while providing reliable open circuit and overpower protection.
3Ease of operation
If prior circuits are used for current control, then basic operation is achieved, but current balancing in parallel LED strings deteriorates
Solution Approach 1:
The patent implements a universal control architecture where a single controller manages multiple LED strings with different configurations (series, parallel, or series-parallel combinations). The system uses standardized PWM output channels and unified current sensing mechanisms that can adapt to various LED string arrangements, providing both ease of operation and reliable current balancing across diverse application scenarios.
Data Source
AI summary
In one embodiment, and LED control circuit may be configured to monitor the value of currents in two or more strings of series connected LEDs, and to adjust the currents to be substantially equal to each other.